2011, Vol.14, No.4, pp.384-390
A two stream model of boron diffusion in silicon has been
developed. The model is intended for simulation of transient
enhanced diffusion including redistribution of ion-implanted boron
during low temperature annealing. The following mechanisms of
boron diffusion were proposed, namely: the mechanism of a
long-range migration of nonequilibrium boron interstitials and the
mechanism due to the formation, migration, and dissolution of the
"impurity atom — silicon self-interstitial" pairs. Based on
the model, simulation of the redistribution of boron implanted
into silicon substrates for annealing temperatures of 800 and 900
Celsius degrees was carried out. The calculated boron
concentration profiles agree well with the experimental data. It
was shown that for a temperature of 800 Celsius degrees the
transport of impurity atoms occurred due to the long-range
migration of nonequilibrium boron interstitials generated during
cluster transformation or dissolution. On the other hand, it was
found that at a temperature of 900 Celsius degrees the pair
diffusion mechanism played a main role in the significant
transient enhanced diffusion. A number of parameters describing
the transport of nonequilibrium boron interstitials and transient
enhanced diffusion of substitutionally dissolved boron atoms were
determined. For example, it was found that at a temperature of 900
Celsius degrees the time-average enhancement of boron diffusion
was approximately equal to 44 times. The results obtained are
important for the development of methods of transient enhanced
diffusion suppression keeping in mind the scaling of the
dimensions of silicon integrated microcircuits.
Key words:
implantation, annealing, diffusion, silicon, boron,
interstitial
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